Inflammatory bowel diseases (IBDs) like Crohn’s disease (CD) and ulcerative colitis (UC) are debilitating diseases that occur when gut microbiota cause inflammation of the epithelial cells in the GI tract. While the exact causes of IBDs remain unknown, researchers believe that both dietary and genetic factors play a role.

Typically, IBDs are treated via surgery or antibiotics. However, these options are often less than ideal. Surgery may be painful and requires extensive recovery time, whereas antibiotics can cause digestion difficulties due to their destruction of essential gut bacteria. As such, less invasive options are under active investigation, many of which focus on dietary manipulation of the gut microbiome to alleviate IBD symptoms. Unfortunately, the majority of such studies have primarily examined older specialty diets rather than attempting to investigate and develop new, more effective therapeutic diets. But in recent years, compelling evidence has begun to emerge in support of more modern dietary interventions for those who seek to alleviate IBD symptoms noninvasively.

Scrutinizing Therapeutic Diets for IBD

For decades, researchers have proposed and evaluated a variety of diets in an attempt to find one that would alleviate the symptoms of IBD. The majority of these diets have focused on modulating the amount of fiber, carbohydrates, and protein consumed by the patient. In a 2013 review, Drs. Jason K. Hou, Dale Less, and James Lewis sought to examine the efficacy of these diets in order to gain greater insight into the possibilities of dietary manipulation of the gut microbiome in IBD patients.

Most IBD diets fall into one of two groups: low fiber diets or high protein diets. However, there is significant overlap between the two, and both are rooted in the belief that IBD patients should avoid providing their compromised gut microbiomes with carbohydrates that could be fermented to cause IBD symptoms. Low fiber diets are thought to accomplish this by denying the body fibrous stool-forming scaffolding to which bacteria can adhere and ferment, causing pain and bloating. High protein diets, in contrast, are believed to work by exploiting the difficulty that gut microbiota of IBD patients have in digesting soluble proteins. Because these soluble proteins require too much energy to break down normally, proponents of high protein diets claim they are not able to produce enough fermented byproducts to cause the symptoms of IBD.

As noted by Drs. Hou, Less, and Lewis, the ideas behind these diets are often based on obsolete or disproven science. For example, an oft-cited study in favor of a low fiber specialty diet was published in 1955 and examined celiac disease rather than IBD. In fact, when analyzing existing literature, the research group concluded that low fiber diets may do more harm than good in patients with IBD, leading to augmentation of IBD symptoms as well as nutritional deficiencies. This may be because fiber is necessary for healthy digestion, and its absence can cause problems independent of IBD symptomatology. High protein diets may also aggravate IBD; while unlikely to cause malnutrition, high protein diets also unlikely to contain enough fiber and carbohydrates to be processed by the GI tract without causing the symptoms of IBD.

The Potential of Low FODMAP Diets

Unlike many others, Drs. Hou, Less, and Lewis didn’t confine their research to older, widely used specialty diets; they also investigated the relatively recently developed FODMAP diet. FODMAPs refers to Fermentable Oligo/Di/Mono-Saccharides And Polyols, which have long been suspected of aggravating IBD symptoms because their molecules are easy for gut microbiota to ferment. In a seminal 2005 paper, the researchers Peter Gibson and Susan Shepherd lent credence to this theory by linking the high quantity of FODMAPs—including fructoses, lactoses, polyols, and oligosaccharides—in the Western diet with the development and aggravation of Crohn’s disease.

FODMAPs are plentiful in the Western diet and particularly prevalent in foods such as fruits, milk, and beans. As a result, the average Westerner consumes more FODMAPs per day than the small intestines’ enzymes are capable of breaking down. The remaining FODMAPs are readily passed through to the large intestines, where they act as “fast food”for bacteria; fermentation of FODMAPs causes bacterial populations to drastically expand, leading to inflammation and tissue damage in the process. This inflammation occurs in the small intestine, large intestine, and the colon, all of which are characteristic of IBD.

As a result of their findings, Gibson and Shepherd patented a preliminary low-FODMAP cookbook. In a 2009 pilot study, they subsequently developed a low-FODMAP diet designed specifically to reduce the symptoms of Crohn’s disease but was broadly applicable to other inflammatory bowel diseases. The study found that most participants who adhered to the low-FODMAP diet strictly for three months experienced improvement in IBD symptoms, whereas those who did not follow the diet strictly saw few improvements. In total, 56% of patients who adhered to the diet saw an overall reduction of symptoms, including diminished bloating, pain, gas, and diarrhea. Many of these improvements were reported to be moderate in magnitude, and study participants were not asked whether they thought that the diet was worth continuing. However, participants generally found the diet to be palatable, easy to prepare, and thus easy to adhere to. Most critically, the success of the low-FODMAP pilot study proved that dietary interventions could offer much-needed relief for IBD patients.

Drs. Hou, Less, and Lewis’ investigation of the FODMAP diet supports these promising results; in fact, the FODMAP diet was found to be more effective for alleviating IBD symptoms than any other dietary intervention they looked at. More recent reviews of the FODMAP diet have also confirmed the therapeutic benefits of the diet in the treatment of IBD. Support for this intervention gives us greater insight into the potential causes of and solutions for IBD symptoms that can help researchers refine treatment methods in the future.

The Future of Diet-Based Therapies for IBD

While the FODMAP diet presents exciting possibilities for noninvasive treatment of IBD, there are still unanswered questions regarding its long-term nutritional impact. While the FODMAP diet is far more nutritionally sustainable than many other specialty diets, unrecognized deficiencies may cause pathologies over extended periods of time. Additionally, the diet may change the gut microbiome in ways that are not yet fully understood and complicate subsequent IBD treatment. As such, longer-term studies are needed to gain more complete insight into the potential of the FODMAP diet. In the meantime, support is emerging for a different kind of dietary intervention: supplementation.

Recent studies suggest that a number of new nutraceutical supplements may help reduce the symptoms of IBD by restoring a healthy gut microbiota in patients with IBD. Butyric acid supplements are considered particularly promising, according to a 2014 paper. Butyric acid is a necessary component of the gut microbiome and is used for cell signaling in the intestinal lumen. Researchers have found that individuals with IBD have lower levels of butyric acid-producing microbiota than in healthy controls, which is believed to be the result of healthy butyric acid-producing bacteria being outcompeted by bacteria farther upstream in the GI tract. As a result, these upstream bacteria are allowed access to an easy food source—potentially FODMAPs—that exacerbates IBD symptoms. Meanwhile, the healthy microbiome further downstream are starved. This leads to the GI tract being deprived of critical butyric acid, thus compromising gastrointestinal function.

The findings of this study indicate that butyric supplements may have a vital role to play in the treatment of IBD. When used alongside specialty diets that carefully regulate the gut microbiome, IBD patients may receive greater symptom relief than they would with diet alone. As more advanced nutritional supplements become available, it may also be possible to use such supplements as standalone treatments. While further research is needed to refine treatment protocols, it is clear that dietary interventions offer exciting possibilities for alleviating IBD symptoms.